Low temperature purification of gases

ABSTRACT

A process for removing the impurities carbon monoxide, carbon dioxide, water vapor and, optionally, hydrogen from a feed stream comprising initially removing water and carbon dioxide, oxidizing carbon monoxide and hydrogen to form carbon dioxide and water vapor, respectively, and removing the oxidation products. The process may be conducted batchwise or continuously by carrying out purification in a plurality of treatment zones wherein one or more zones are being regenerated while one or more others are purifying the feed stream.

FIELD OF THE INVENTION

The present invention relates generally to a process for the productionof high purity gases at low temperatures and, particularly, to acontinuous process of removing carbon dioxide, carbon monoxide, hydrogenand water vapor from a gas mixture, preferably air.

BACKGROUND OF THE INVENTION

High purity gases such as nitrogen in which impurities are present inamounts well below part per million levels are required in themanufacture of integrated circuits to prevent defects in chips ofincreasing line densities. Cryogenic distillation is typically used forthe production of highly purified nitrogen gas.

Removal of impurities from the feed gas for cryogenic distillation isrequired for the production of high purity nitrogen. When air is used asthe feed gas, impurities, such as H₂ O and CO₂, have to be removed toprevent freeze-up in the low temperature sections of the plant whileother impurities, such as H₂ and CO, have to be removed to preventcontamination of the nitrogen product.

A two-step procedure has been employed for the removal of theseimpurities from air in a nitrogen production process. In the first step,a compressed feed gas is heated to temperatures between 150° to 250° C.and then contacted with a catalyst to oxidize CO to CO₂ and H₂ to H₂ O.Noble metal catalysts, typically based on platinum, are commonly usedfor the oxidation step. In the second step, the oxidization products,CO₂ and H₂ O, are removed from the compressed gas stream either by atemperature-swing adsorption process (see K. B. Wilson, A. R. Smith andA. Theobald, IOMA BROADCASTER. Jan.-Feb. 1984, pp 15-20) or by apressure-swing adsorption process (see M. Tomonura, S. Nogita, KagakuKogaku Ronbunshu, Vol. 13, No. 5, 1987, pp 548-553).

These processes, although effective, are disadvantageous for thecommercial scale production of highly purified gases, particularlynitrogen gas due to their high cost of operation. The cost of operationis high because of the extensive use of expensive noble metal catalysts.In addition, separate vessels must be used for the catalytic treatmentstep and the adsorption step to remove the impurities. In addition, heatexchangers are required to both heat the gas as it passes into thecatalyst vessel and cool the effluent therefrom. This poses additionalcosts, both in terms of equipment and energy.

Low temperature processes for removing parts per million levels ofimpurities from inert gas streams are also known in the art. Weltmer etal., U.S. Pat. No. 4,579,723, discloses passing an inert gas streamcontaining nitrogen or argon through a catalytic bed containing amixture of chromium and platinum on gamma-alumina and a second bedcomposed of a mixture of several metals mounted on gamma-alumina. Thebeds effectively convert carbon monoxide to carbon dioxide and hydrogento water vapor and adsorb the resulting impurities to produce a productstream containing total impurities of less than 1.0 part per million.

Tamhankar et al., U.S. Pat. No. 4,713,224, discloses a one-step processfor purifying gases containing minute quantities of CO, CO₂, O₂, H₂ andH₂ O in which the gas stream is passed through a particulate materialcomprised of nickel having a large surface area.

Processes for the ambient temperature conversion of carbon monoxide tocarbon dioxide have also been described as, for example, by Tamura etal., U.S. Pat. No. 3,672,824, and Frevel et al., U.S. Pat. No.3,758,666.

None of these processes, however, provide an integrated low temperaturesystem in which a feed stream which contains up to significant amountsof impurities can be treated in an efficient and inexpensive manner toobtain highly purified gaseous products which can be subsequentlytreated to produce high purity gases, such as nitrogen.

It is, therefore, an object of the present invention to provide aprocess for producing highly purified gaseous products from a feedstream containing up to significant amounts of impurities.

It is another object of the invention to provide a process for purifyingoxygen-containing gas streams suitable for the production of highlypurified nitrogen by cryogenic distillation.

SUMMARY OF THE INVENTION

The present invention is generally directed to a process for producing asubstantially pure gaseous product from a feed stream containing theimpurities carbon monoxide, carbon dioxide, hydrogen and water vaporand, particularly, to the treatment of feed streams which contain morethan minute amounts of such impurities. The process comprises removingwater vapor, if present from the feed stream, contacting the feed streamwith an oxidation catalyst to thereby convert the carbon monoxidepresent to carbon dioxide and the hydrogen present to water vapor. Thewater vapor and carbon dioxide obtained from the oxidation step and anyother carbon dioxide and water vapor present are thereafter removed fromthe stream. The resulting gaseous product is substantially free of theseimpurities, generally containing no more than about one ppm of carbondioxide and a combined total of the other impurities not exceeding aboutone ppm.

The gaseous feed is preferably treated in a single treatment zone,preferably contained in a single vessel which includes a firstadsorption section, a catalysis section and a second adsorption section.The first adsorption section contains one or more beds of awater-removing adsorbent, such as activated alumina, silica gel,zeolites or combination thereof. The catalysis section containsrelatively low cost catalysts for the catalytic conversion of carbonmonoxide to carbon dioxide and hydrogen to water vapor. The formercatalyst is preferably a mixture of manganese and copper oxides, whilethe latter catalyst is preferably supported palladium. If the amount ofhydrogen in the gaseous feed is such that its continued presence is notdetrimental to the intended use of the purified product, then thecatalyst for converting hydrogen to water vapor may be omitted. This canoccur, for example, when the purified product is used for maintaining aninert environment in the production and storage of pharmaceuticals. Onthe other hand, the production of highly purified gas used in themanufacture of very high density computer chips will require the removalof even the minute amount of hydrogen typically present in air. Inaccordance with the present invention, such amounts of hydrogen can beremoved by converting hydrogen to water vapor using supported palladiumor other suitable oxidation catalyst in the catalysis section.

The present process may be conducted either batchwise or continuously.In either case, the treatment zone containing the two adsorptionsections and the catalysis section must be periodically regenerated bypurging the accumulated adsorbed impurities. In a batchwise system,purification of the gas feed must be stopped during regeneration of thetreatment section. In the continuous system, a plurality of treatmentzones are used with at least one treatment zone producing purified gaswhile at least one other treatment zone is undergoing regeneration.

In accordance with the present invention, the treatment zones may beregenerated by a purge gas at near feed temperatures or at elevatedtemperatures in a temperature-swing mode. The resulting gaseous productshave no more than about one ppm carbon dioxide and no more than aboutone ppm total of other impurities. The process of the present inventionis particularly suited for purifying air to obtain a feed gas suitablefor the production of highly purified nitrogen gas by cryogenicdistillation.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings in which like reference characters indicate likeparts are illustrative of embodiments of the invention and are notintended to limit the scope of the invention as encompassed by theclaims forming part of the application:

FIG. 1 is a schematic view of one embodiment of the invention showing acontinuous process for the production of highly purified gas utilizing apressure-swing mode of operation;

FIG. 2 is a schematic view of another embodiment of the invention,similar to that of FIG. 1, in which a temperature-swing mode ofoperation is utilized; and

FIG. 3 is a schematic view of the embodiment of the invention shown inFIG. 2 showing further treatment of the highly purified gaseous productin a cryogenic distillation system.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention produces a highly purified gaseousproduct with regard to four impurities, i.e. carbon monoxide, carbondioxide, hydrogen and water vapor. It is to be understood that the term"impurities"as utilized herein, refers to these gases and does notinclude other gases such as, for example, trace amounts of hydrocarbons,which might be present in a feed gas mixture and which may otherwise beregarded as impurities.

It is further to be understood that the feed gas mixture contemplatedherein contains at least one impurity of carbon monoxide and hydrogen.Carbon dioxide and water vapor may also be present either in the initialfeed stream or may be generated during the oxidation step of theprocess. It is further necessary that the feed stream contain oxygen forthe catalytic conversion of carbon monoxide and hydrogen as contemplatedherein. In the event that the feed stream entering the oxidation stepdoes not contain sufficient oxygen, oxygen may be added thereto in theform of highly purified oxygen, oxygen-enriched air or the like.

Referring to the drawings, and particularly to FIG. 1, there is shown acontinuous process for the production of purified gas in which thetreatment zone undergoing regeneration is purged with a gas at near thetemperature of the gas feed.

A feed gas stream, as for example atmospheric air, is passed via a line2 to a compressor 4 wherein the gas is compressed to about 75 to 150psig. The compressed gas stream is then sent via a line 6 to a heatexchanger 8 wherein it is cooled prior to introduction via line 10 intoa water separator 12 to remove liquid water therefrom. The effluent fromthe water separator 12 is at a temperature of from about 5° C. to 50°C., preferably from about 20° C. to 45° C.

The gas is sent via a line 14 through a valve 16 and a line 20 to atreatment zone 29 within a single vessel 30 which contains a loweradsorption section 34, a catalysis section 38, and an upper adsorptionsection 42.

The lower adsorption section 34 contains at least one bed of awaterremoving adsorbent material such as activated alumina, silica gel,zeolites or combinations thereof which removes water vapor and some ofthe carbon dioxide present in the compressed gas stream. Most of thewater vapor remaining in the compressed gas must be removed in the loweradsorbent section 34 in order to prevent deactivation of the oxidationcatalysts present in the catalysis section 38 and to permit lowtemperature processing of the feed. Preferably, the adsorption section34 comprises a predominant layer of activated alumina or silica gel anda layer of zeolite, for example, Zeolite 13X or 5A manufactured by UOP,Inc.

The gas stream then enters the catalysis section 38 within the treatmentvessel 30. The physical separation of the three sections of thetreatment vessel 30 is effected by means well known in the art. Forexample, the adsorption section 34 and the catalysis section 38 may beseparated by a stainless steel screen which may also be employed toseparate the catalysis section from the upper adsorption section 42.

The catalysis section 38 contains catalysts for the oxidation of carbonmonoxide to carbon dioxide and for the conversion of hydrogen to watervapor. The catalysts used for eliminating carbon monoxide are preferablymetal oxides such as nickel oxide or a mixture of the oxides ofmanganese and copper. The catalysts used to oxidize hydrogen to watervapor are preferably supported palladium and other noble metal catalystsknown in the art. Preferably, the gas stream contacts the carbonmonoxide oxidation catalysts prior to the hydrogen oxidation catalysts.

The thus-treated gas enters the upper adsorption section 42 for removalof carbon dioxide and water vapor. Adsorbents that may be used in theupper adsorption section 42 preferably include zeolites, activatedalumina, silica gel and combinations thereof.

The thus treated purified gas containing no more than about 1.0 ppmcarbon dioxide and no more than about one ppm of the total of otherimpurities is withdrawn from the treatment vessel 30 through a line 46and a valve 58 to a line 62 where it is sent to storage or for furtherprocessing such as by a cryogenic distillation facility.

At the same time the treatment zone 29 is purifying the gas feed, atreatment zone 31 is undergoing regeneration to remove accumulatedimpurities. The treatment vessel 32 is essentially the same as treatmentvessel 30 and contains a corresponding lower adsorption section 36, acatalysis section 40 and an upper section 44. The structure of the threesections 36, 40, 44 and the materials contained therein are the same asdescribed above for the sections 34. 38, 42, respectively.

After purifying the feed gas for a period of time, each of the lower andupper adsorption sections 36 and 44 become contaminated with carbondioxide and water, and the catalysis section 40 accumulates smallamounts of carbon monoxide and hydrogen. These impurities are removed bypurging the vessel 32 with a gas which does not adversely affect thecatalyst and is free of the impurities that are to be removed from thevessel 32. For example, if the feed gas is air, a suitable purge gas canbe highly purified nitrogen, oxygen or mixtures thereof.

Prior to introduction of the purge gas, the vessel 32 is vented toreduce the pressure therein to close to atmospheric. This is carried outby opening valve 26 thereby venting through line 22 and exit line 28.Referring further to FIG. 1, a purge gas obtained from an independentsource (not shown), as a side stream from the line 62, or as a waste gasfrom a cryogenic distillation column at a pressure of from about 1-5psig is fed via a line 70 to an optional blower 68 where the pressuremay be raised, if necessary. The gas flows via the line 66 to a line 54and through a valve 52 into a line 48 where the purge gas enters thevessel 32.

The purge gas exits the vessel 32 through a line 22 and flows through avalve 26 and is thereafter discharged via a line 28. During thisoperation, the valve 24 connected to the line 20 is closed. Afterpurging, it is preferred to gradually build up the pressure in thevessel 32 with a purified gas, referred to as "product backfill" inTABLE I. This repressurizing may be accomplished by diverting a smallportion of the purified gas from the line 46 through the valve 56 andinto the vessel 32 via the line 48.

Once purging and repressurization are completed, the vessel 32 is againready to begin a purification cycle. This is done by closing the valve16 and opening the valve 18 so that the gas stream flows from the line14 to the line 22 and into the lower adsorption section 36 of the vessel32. The purified gas obtained from the vessel 32 passes through the line48 and a valve 60 into the exit line 62. At the same time, the flow ofthe feed stream to the vessel 30 is terminated by closing the valve 16and regeneration is commenced by first venting the vessel 30 and thenintroducing the purge gas via lines 66, 54, and valve 50 into the line46.

The time for completing a cycle in the pressure-swing mode of operationis typically from about 6 to 40 minutes. The cycle for the two-vesselprocess described in FIG. 1 is shown in TABLE I.

                  TABLE I                                                         ______________________________________                                                                 Valves    Typical                                    Step                     Open      Time (sec)                                 ______________________________________                                        a.   Purify using vessel 30, vent ves-                                                                 16, 26, 58                                                                              30                                              sel 32 to atmosphere                                                     b.   Purify using vessel 30, regenerate                                                                16, 26, 52,                                                                             510                                             vessel 32 with impurity-free gas                                                                  58                                                   c.   Purify using vessel 30, backfill                                                                  16, 56, 58                                                                              60                                              vessel 32 with vessel 30 product                                         d.   Purify using vessel 32, vent ves-                                                                 18, 24, 60                                                                              30                                              sel 30 to atmosphere                                                     e.   Purify using vessel 32, regenerate                                                                18, 24, 50,                                                                             510                                             vessel 30 with impurity-free gas                                                                  60                                                   f.   Purify using vessel 32, backfill                                                                  18, 56, 60                                                                              60                                              vessel 30 with vessel 32 product                                                                  Total Time:                                                                             20 minutes.                                ______________________________________                                    

The process of the present invention can also be carried out by heatingthe purge gas to temperatures well above the temperature of the feedstream. In this temperature-swing mode of the operation, the temperatureof the feed gas is cooled to generally below the temperature of the feedgas employed in the pressure-swing embodiment, preferably in the rangeof from about 5° to 20° C.

Referring to FIG. 2, the temperature-swing mode of operation commencesby pressurizing the feed gas stream in the compressor 4 to a pressure offrom about 75 to 150 psig. The compressed gas stream is then passed to aheat exchanger 8 through the line 6 and then to the water separator 12though the line 10. The compressed gas exiting the water separator 12 ispreferably at a temperature of from about 5° to 20° C. The operation ofthe treatment section 29 is the same as that described in connectionwith the embodiment of FIG. 1.

In the temperature-swing mode of operation shown in FIG. 2, the vessels30 or 32 are normally pressurized slowly using part of the feed gas asopposed to product backfill as described in the pressure-swing mode ofoperation. For the repressurization of vessel 30, the valve 16 will beopen while valve 18 is utilized for the repressurization of the vessel32. After the repressurization of the vessel 30, purification of thefeed gas takes place and the highly purified product is sent via theline 62 for downstream processing in, for example, a cryogenicdistillation system. During purification in the vessel 30, the vessel 32is first vented through the valve 26 and the line 28 and thenregenerated using impurity-free purge gas which is passed to theoptional blower 68 and then to a heater 64 via the line 66.

The temperature of the purge gas entering the system through line 70 isgenerally close to that of the feed gas. Therefore, the purge gas isheated in the heater 64, preferably to a temperature of from about 80°to 250° C. The heated regeneration gas passes through the line 54, theopen valve 52 and the line 48 to vessel 32 and then to the line 28 viathe open valve 26, thereby removing previously adsorbed impurities.

The heat supplied to the vessel 32 by the purge gas must be sufficientto desorb the impurities contained therein. Accordingly, it ispreferable to turn off the heater 64 after sufficient heat has beenintroduced into the vessel 32. The amount of heat required for a givenvessel can be routinely determined. The flow of purge gas continuesafter heater 64 has been turned off to remove desorbed impurities and tobegin to cool the vessel 32 in preparation for the next purificationstep. After the vessel 32 is cooled sufficiently, it is slowlyrepressurized using a portion of the feed gas through the open valve 18and the line 22. The vessel 30 continues to purify the feed gas duringthis time. After repressurization of the vessel 32, the vessel 30undergoes the steps of venting, heating with purge gas and cooling withpurge gas as described for the vessel 32. Simultaneously, the vessel 32is purifying feed gas. The process can run continuously in this manner.

The complete cycle time for the temperature-swing process described inFIG. 2 normally is from about 8 to 24 hours, much longer than the cycletimes for the pressure-swing mode of operation. A complete cycle for atwo-bed process operated in the temperature-swing mode is given in TABLEII below.

                  TABLE II                                                        ______________________________________                                                                           Typical                                                             Valves    Time                                       Step                     Open      (hours)                                    ______________________________________                                        a.   Pressurize vessel 30 with feed,                                                                   16, 18, 60                                                                              0.25                                            purify using vessel 32                                                   b.   Purify using vessel 30, vent ves-                                                                 16, 26, 58                                                                              0.25                                            sel 32 to atmosphere                                                     c.   Purify using vessel 30, regenerate                                                                16, 26, 52,                                                                             2.5                                             vessel 32 with hot purge gas                                                                      58                                                   d.   Purify using vessel 30, cool ves-                                                                 16, 26, 52,                                                                             5.0                                             sel 32 with purge gas                                                                             58                                                   e.   Purify using vessel 30, pressurize                                                                16, 18, 58                                                                              0.25                                            vessel 32 with feed                                                      f.   Purify using vessel 32, vent ves-                                                                 18, 24, 60                                                                              0.25                                            sel 30 to atmosphere                                                     g.   Purify using vessel 32, regenerate                                                                18, 24, 50,                                                                             2.5                                             vessel 30 with hot purge gas                                                                      60                                                   h.   Purify using vessel 32, cool ves-                                                                 18, 24, 50,                                                                             5.0                                             sel 30 with purge gas                                                                             60                                                   ______________________________________                                    

As previously described in connection with FIG. 1, the purge gas shouldbe free of the impurities to be removed by the system (i.e.substantially free of carbon monoxide, carbon dioxide, hydrogen andwater vapor) and should not adversely affect the components of the threesections of the vessel. If the purified gas exiting the line 62 is sentto a cryogenic distillation system for further processing, the waste gasexiting the cryogenic system may be advantageously used as the purgegas.

A system for transferring the purified gas to a cryogenic distillationsystem is shown in FIG. 3. The purified gas stream exiting at line 62 iscooled in an exchanger 76 against the returning product streams 78 and86 and the purge gas stream 80. The warmed product streams 72 and 74 aretaken as products and sent to user equipment or storage. The warm purgegas stream 70 is used to regenerate the purification vessels asmentioned earlier. The cold feed gas stream 82 exiting the exchanger 76is further cooled in a turboexpander 84 to produce a stream 88 which iscryogenically distilled in a column 90 to produce two product streams 86and 78 and a waste stream 80 which is used as the purge gas.Modifications and additions of conventional cryogenic distillationsystems would be apparent to those skilled in the art.

EXAMPLE I

A single-vessel process was operated in the pressure-swing mode as shownin FIG. 1. The first bed contained an initial layer of 27 lbs. of acommercially available activated alumina, then a layer of 1.7 lbs. of6×14 mesh Hopcalite (a mixture of manganese and copper oxidesmanufactured by MSA of Pittsburgh, Pa.) and a final layer of 11.6 lbs.of the activated alumina. Water-saturated feed air at a temperature of25° C., a pressure of 140 psig, a flow rate of 23.0 std. cubic feet permin., and containing about 350 ppm CO₂ was passed through the vesselusing the cycle sequence shown in TABLE I. Carbon monoxide at acontrolled flow rate was blended in the feed air to give a feed gasstream carbon monoxide concentration of 5.5 ppm. The vessel wasregenerated at the feed temperature (25° C.) using impurity-freenitrogen at an average flow rate (averaged over the entire cycle) of 9.7std. cubic feet per sec.

The gas exiting the vessel contained less than 0.1 ppm H₂ O, 1 ppmcarbon dioxide and no carbon monoxide. The carbon monoxide in the feedair was converted to carbon dioxide by the Hopcalite layer and theremaining carbon dioxide and the oxidation products were removed by thesecond activated alumina layer.

EXAMPLE II

A single vessel similar to that in Example I was loaded with a firstlayer of 27 lbs. of commercially available activated alumina, a secondlayer of 1.7 lbs. of 6×l4 mesh Hopcalite, a third layer of 1.5 lbs. of acatalyst containing 0.5% by weight palladium supported on alumina(manufactured by Engelhard Corporation) and a final layer of 10 lbs. ofactivated alumina. The process was operated under the same conditions ofExample I with the feed air containing 5.5 ppm of added CO and 2.0 ppmof added hydrogen in addition to the amounts of H₂ O and CO₂ stated inExample I. The gas exiting the vessel contained no H₂, no CO, less than0.1 ppm of H₂ O and less than 1 ppm of carbon dioxide.

EXAMPLES III-VI

The process of the present invention was conducted in accordance withthe scheme shown and described in FIG. 2 wherein the purge gas washeated to a temperature exceeding the temperature of the feed gas air.

The lower adsorption section 34 of the vessel 30 was charged with alayer of 11.5 lbs. of activated alumina having thereon a layer ofZeolite 13X in an amount of 5.7 lbs. The catalysis section 38 wascharged with 1/8" Carulite 200 pellets (a mixture of manganese andcopper oxides manufactured by Carus Chemical Company of Ottawa, Ill.) inthe amounts shown in TABLE IV. The upper adsorption section 42 wasprovided with 5.4 lbs. of Zeolite 13X.

A water-saturated air stream pressurized to 80 psig containing about 350ppm of carbon dioxide and varying amounts of carbon monoxide wasforwarded to the vessel 30 at the rate of 28.8 standard cubic feet permin. Simultaneously, a regeneration flow of a purge gas at the rate of5.1 standard cubic feet per min. was used to remove impurities from thevessel 32. At a feed temperature of 4.4° C., a regeneration gastemperature of 121° C., was utilized. Using a higher feed temperature of12.5° C., a regeneration gas temperature of 148.9° C. was utilized.

The time necessary to perform each step of the purification andregeneration cycles is shown in TABLE III.

                  TABLE III                                                       ______________________________________                                        Step                 Time (hr.)                                               ______________________________________                                        Vessel pressurization   0.2                                                   Feed purification       6.0                                                   Vessel venting          0.1                                                   Heating with impurity-free nitrogen                                                                   3.5                                                   Cooling with impurity-free nitrogen                                                                   2.2                                                   Total                   12.0   hrs.                                           ______________________________________                                    

As seen from TABLE III, the time necessary to complete a single cycle ofpurification and regenertion is 12.0 hrs. during the temperature-swingadsorption mode or approximately twenty times longer than the timeneeded to complete a single cycle in the pressure-swing adsorption modeof operation.

TABLE IV shows that in each of EXAMPLES III-VI, the conversion of carbonmonoxide to carbon dioxide is very high. This is accomplished at verylow feed temperatures in accordance with the present invention in partbecause substantially all of the water vapor has been removed.

                  TABLE IV                                                        ______________________________________                                                Feed    Feed CO   Amount of                                                                             Av. Conversion                              Example Temp.   Conc.     Carulite                                                                              of CO to CO.sub.2                           Number  (°F.)                                                                          (ppm)     (lbs.)  (%)                                         ______________________________________                                        III     40.0    9.0       3.0      92.0                                       IV      40.0    4.9       3.0      95.0                                       V       54.5    4.9       3.0     100.0                                       VI      40.0    4.9       4.5     100.0                                       ______________________________________                                    

In all examples, the gas exiting the lower adsorption section containedless than 0.1 ppm of water vapor and the gas recovered from the upperadsorption section contained less than 1 ppm carbon dioxide.

I claim:
 1. Process for producing a gaseous product substantiallypurified from impurities consisting of water vapor, carbon monoxide,carbon dioxide and hydrogen, said process comprising:(a) removing watervapor from a gaseous feed stream containing said impurities andsufficient oxygen to convert all carbon monoxide and hydrogen present insaid gaseous feed stream to carbon dioxide and water; (b) contacting thefeed stream from step (a) with one or more oxidation catalysts tothereby convert carbon monoxide to carbon dioxide and hydrogen to watervapor; and (c) removing water vapor and carbon dioxide from the gaseousproduct obtained in step (b) to obtain said substantially purifiedgaseous product.
 2. The process of claim 1, wherein step (a) comprisescontacting the gaseous feed stream with a water vapor-removingadsorbent.
 3. The process of claim 2, wherein the water vapor-removingadsorbent is selected from the group consisting of activated alumina,silica gel, zeolites and combinations thereof.
 4. The process of claim1, wherein the oxidation catalyst for converting carbon monoxide tocarbon dioxide is a mixture of manganese and copper oxides.
 5. Theprocess of claim 1, wherein the oxidation catalyst for convertinghydrogen to water vapor is supported palladium.
 6. The process of claim1, wherein the substantially pure gaseous product contains no more than1.0 ppm of carbon dioxide and no more than a total of 1 ppm of saidother impurities.
 7. The process of claim 1, wherein the gaseous feedstream is air.
 8. The process of claim 1, wherein the feed stream iscompressed to a pressure of from about 75 to 150 psig prior to step (a).9. The process of claim 1, wherein steps (a)-(c) are conducted in asingle treatment zone containing separate sections for carrying out eachof said steps.
 10. The process of claim 9, wherein steps (a)-(c) areconducted in a plurality of treatment zones, at least one of saidtreatment zones being used to remove said impurities from said gaseousfeed stream and at least one of said treatment zones beingsimultaneously purged to remove said impurities contained therein. 11.The process of claim 10, wherein the step of purging said treatment zonecomprises reducing the pressure in said treatment zone, and passing apurge gas therethrough at a pressure below the pressure of the feedstream and at ambient temperature to the treatment zone, said purge gasbeing substantially free of said impurities.
 12. The process of claim10, wherein the step of purging the treatment zone comprises reducingthe pressure therein and passing a purge gas therethrough at atemperature in the range of from about 80° to 250° C., said purge gasbeing substantially free of said impurities.
 13. The process of claim 12further comprising passing an additional amount of purge gas through thetreatment zone to reduce the temperature thereof.
 14. The process ofclaim 1 wherein said gaseous feed steam is at a temperature in the rangeof about 5° C. to about 50° C.
 15. The process of claim 1 wherein saidgaseous feed stream is at a temperature in the range of about 20° C. toabout 45° C.
 16. The process of claim 7 further comprising the step ofcryogenically separating the components of the product of step (c). 17.Process for producing a gaseous product substantially purified fromimpurities consisting of water vapor, carbon monoxide and carbon dioxidecomprising:(a) removing water vapor from a gaseous feed streamcontaining said impurities and sufficient oxygen to convert all carbonmonoxide present in said gaseous feed stream to carbon dioxide; (b)contacting the feed stream from step (a) with one or more oxidationcatalysts to thereby convert carbon monoxide to carbon dioxide; and (c)removing carbon dioxide and any remaining water vapor from the gaseousproduct obtained in step (b) to obtain said substantially purifiedgaseous product.
 18. The process of claim 17, wherein step (a) comprisescontacting the gaseous feed stream with a water vapor-removingadsorbent.
 19. The process of claim 18, wherein the water vapor-removingadsorbent is selected from the group consisting of activated alumina,silica gel, zeolites and combinations thereof.
 20. The process of claim17, wherein the oxidation catalyst in step (b) is a mixture of manganeseand copper oxides.
 21. The process of claim 17, wherein thesubstantially pure gaseous product contains no more than 1.0 ppm ofcarbon dioxide and no more than a total of 1 ppm of said otherimpurities.
 22. The process of claim 17, wherein the gaseous feed streamis air.
 23. The process of claim 17, wherein the feed stream iscompressed to a pressure of from about 75 to 150 psig prior to step (a).24. The process of claim 17, wherein steps (a)-(c) are conducted in asingle treatment zone containing separate sections for carrying out eachof said steps.
 25. The process of claim 24, wherein steps (a)-(c) areconducted in a plurality of treatment zones, at least one of saidtreatment zones being used to remove said impurities from said gaseousfeed stream and at least one of said treatment zones beingsimultaneously purged to remove said impurities contained therein. 26.The process of claim 25, wherein the step of purging said treatment zonecomprises reducing the pressure in said treatment zone, and passing apurge gas therethrough at a pressure below the pressure of the feedstream and at ambient temperature to the treatment zone, said purge gasbeing substantially free of said impurities.
 27. The process of claim25, wherein the step of purging the treatment zone comprises reducingthe pressure therein and passing a purge gas therethrough at atemperature in the range of from about 80° to 250° C., said purge gasbeing substantially free of said impurities.
 28. The process of claim 27further comprising passing an additional amount of purge gas through thetreatment zone to reduce the temperature thereof.
 29. The process ofclaim 17 wherein said gaseous feed stream is at a temperature in therange of about 5° C. to about 50° c.
 30. The process of claim 17 whereinsaid gaseous feed stream is at a temperature in the range of about 20°C. to about 45° C.
 31. The process of claim 22 further comprising thestep of cryogenically separating the components of the product of step(c).